Technical rarity Swiss silver open faced watch Circa 1793

Rare silver verge for the English market
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A silver case with hallmarks London, English watch paper, signed verge movement, circa 1793.
Enamel dial in perfect condition, decentralized time indication, retrograde English weekdays, retrograde date, very beautiful condition, a technical rarity.
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Diameter:  55 mm   Weight: 120 g
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Signed:  Houriet